(1) Field of the Invention
The present invention relates to a double. ended direct-feed type writing implement having writing points (point assemblies) on both ends of the barrel.
(2) Description of the Prior Art
A typical, so-called double ended writing implement incorporates an ink absorbent element inside its ink tank with the whole ink inside the ink tank being absorbed in the ink absorbent element. The writing implement of this type has advantages in being assembled easily, but because ink absorbed in the sliver moves down due to gravity, much ink ejects out from one of the writing points (point assemblies) while extremely less amounts of ink eject out from the other writing point (point assembly), causing thinning of lines and ink starving.
Since an ink absorbent element in this type of pen makes use of capillarity, the ejected amount of ink gradually decreases as writing continues, so it is impossible to provide stable and consistent ink ejection until ink end or the last drop of ink.
Further, while a direct-feed type writing implement makes it possible to monitor the residual quantity of ink, a writing implement using an ink absorbent element cannot allow the residual quantity of ink to be seen. In order to solve the above problems and drawbacks of the double ended writing implements using an ink absorbent element, there has been an idea that the ink is made to directly fill the ink tank without any ink absorbent element and two ink collectors, which prevent ink leakage due to air expansion inside the ink tank caused by decrease in pressure and increase in temperature, are arranged on both ends. In this case, each ink collector needs to have an air/liquid exchanger allowing air to enter the ink tank as ink is consumed. In the state where both the caps to be placed on both ends of the ink tank are off, the air/liquid exchanger positioned at the top cannot be closed because the ink moves down pooling in the bottom inside the ink tank. Therefore, the interior and exterior of the ink tank communicate with each other through this air/liquid exchanger so that air flows into the ink tank via the air/liquid exchanger. As a result, the weight of ink or ink head directly acts on the writing point (point assembly) at the writing end, causing so-called forward leakage, i.e., ink to leak out from the writing point (point assembly), staining the paper surface, clothes and the like. If the cap has a sealing configuration, the sealing surface may be damaged, soiled with dirt and dust. In such a case, sealing becomes imperfect, causing the same problem, i.e., forward leakage.
Japanese Utility Model Application Laid-Open Hei 6 No.20084 discloses an arrangement which fills the ink tank with ink without using any ink absorbent element by letting an ink collector prevent ink leakage due to air expansion inside the ink tank due to decrease in pressure and increase in temperature. This specification discloses a double ended direct-feed type writing implement. The embodiment of this disclosure uses an ink collector arranged around the ink tank so it has the drawback that the residual quantity of ink inside the ink tank cannot be monitored. Even with a transparent ink collector, if this ink collector actually functions against decrease in pressure or increase in temperature, having been wetted with ink, it is difficult to see the residual quantity of ink.
Another known conventional example of double ended writing implement has an ink tank with two sections divided by a partition therein, each having an individual writing point (point assembly). With this configuration, if one writing point(point assembly) is used more frequently than the other, the ink inside the ink tank for the more frequently used writing point will be used up earlier, so that the usability of the double ended writing implement, that is, capability of using both writing points (point assemblies), cannot be obtained. In some cases, the writing implement might be discarded because of one of the tips is used up, resulting in poor economy.
Further, in general, direct-feed type writing implements, if the ink tank is affected by heat or reduction in pressure, air inside ink tank expands, and this expanded air forces ink out of the pen. This is why the ink collector is provided so as to prevent ink leakage outside the pen. However, there is a problem that the ink may leak out of the pen, causing ejection or flooding of ink if an air expansion is too large beyond the retaining capability of the ink collector.
It is therefore an object of the present invention to provide a double ended direct-feed type writing implement with an ink tank directly filled up with ink, still free from the above problems.
More specifically, the object of the invention is to provide a double ended direct-feed type writing implement which allows the residual quantity of ink to be monitored, assures a stable and consistent ink flow until ink end, and enables continuous flow of ink from both ends until the ink inside the ink tank is fully used up. A further object of the present invention is to provide a double ended direct-feed type writing implement which is free from the forward leakage problem which would occur when ink collectors are provided at both ends of the ink tank.
Still more, it is an object of the present invention to provide a double ended direct-feed type writing implement which is prevented from ink election or flooding due to decrease in pressure and increase in temperature of the ink tank, which is the problem inherent in writing implements of a direct-feed type.
The present invention has been devised to attain the above objects, and the present invention is configured as follows:
In accordance with the first aspect of the present invention, a double ended direct-feed type writing implement includes: an ink tank; a pair of writing points (point assemblies) as writing elements, arranged both ends of the ink tank; an ink collector, provided for each writing point, and having an air/liquid exchanger for adjusting the internal pressure inside the ink tank by making use of capillarity; an ink feeder means, provided for each writing point, and including a center core for feeding ink to the writing point (point assembly); and means for inhibiting air from flowing into the ink tank through the ink collector air/liquid exchanger located at the top while the pen is unused for writing.
In accordance with the second aspect of the present invention, the double ended direct-feed type writing implement having the above first feature is characterized in that one feeder means including a center core and the like is connected to the other.
In accordance with the third aspect of the present invention, the double ended direct-feed type writing implement having the above first feature is characterized in that an ink tank partitioning element is formed inside the ink tank and the feeder means including a center core and the like is extended to the ink storage pool created by the ink tank partitioning element.
In accordance with the fourth aspect of the present invention, the double ended direct-feed type writing implement having the above first feature is characterized in that an ink tank partitioning element with a passage hole formed therein is formed inside the ink tank, and the ink feeder means is penetrated through the passage hole of the ink tank partitioning element.
In accordance with the fifth aspect of the present invention, the double ended direct-feed type writing implement having the above first feature is characterized in that the ink collector space of one ink collector and that of the other ink collector are connected to each other by way of an air flowing passage.
In accordance with the sixth aspect of the present invention, the double ended direct-feed type writing implement having the above first feature is characterized in that at least one of the writing points (point assemblies) is of a ball-point type, and the ball-point type writing point (point assembly) has a spring inserted into the bore thereof and pressing the rear side of the writing ball rotatably held at the front part thereof , whereby the writing ball is abutted in fluid-tight contact with the inner brim of the ball holding portion of the point assembly to prevent outflow of ink.
In accordance with the seventh aspect of the present invention, the double ended direct-feed type writing implement having the above first feature is characterized in that at least one end of the writing points comprised of a joint which is connected to the rear end of the writing point (point assembly) and has a valve chamber at the rear thereof, the valve chamber having a tapered or spherical ball valve seat in the rear thereof and idly holding a ball valve therein, and when the writing point (point assembly) is set upward, the ball valve is in close contact with the ball valve seat so as to close the conduit fluid-tightly to thereby prevent backward leakage of ink, and when the writing point (point assembly) is set downwards, the hermetic contact state is released so as to allow ink to flow into the writing point (point assembly).
In accordance with the eighth aspect of the present invention, the double ended direct-feed type writing implement having the above first feature is characterized in that a fine hole is formed between the ink collector space of each ink collector and the ink conduit hole in which the ink feeder means including a center core and the like is disposed.
In accordance with the ninth aspect of the present invention, the double ended direct-feed type writing implement having the above first feature is characterized in that the ink feeder portion for leading ink held in the ink feeder means or in the ink absorbent element is connected to the air/liquid exchanger.
The double ended direct-feed type writing implement of the present invention has the means for inhibiting air from flowing into the ink tank through the ink collector air/liquid exchanger located at the top while the pen is unused for writing. Therefore, this configuration inhibits forward leakage from the writing point (point assembly) located at the bottom due to inflow of air from the collector air/liquid exchanger at the top while the pen is unused for writing. More specifically, since the feeder means such as a center core etc., is able to lead ink to the air/liquid exchanger located at the top, an ink meniscus is formed around the exchanger, thus making it possible to prevent air inflow through the collector air/liquid exchanger at the top.
Since the writing implement of the present invention can use direct-feed type liquid ink, the residual quantity of ink can be monitored while stable and consistent ink ejection can be obtained until the ink end or the last drop of ink.
Further, since ink in the ink tank can be supplied to both writing points (point assemblies), both the writing points (point assemblies) can continue to be able to deliver ink without causing any ink starving in only one of them until the ink inside the ink tank is fully used up.
Additionally, since the ink collector-space of one ink collector is connected to that of the other ink collector by way of the air flowing passage, it is possible to reduce ink ejection or flooding due to expansion of air inside the ink tank, which is caused by decrease in pressure, increase in temperature and the like.
Finally, provision of a spring urging the rear side of the writing ball, provision of a joint idly holding a ball valve therein and/or provision of an ink feeder portion are effective in preventing forward leakage.